(CNN) – Ahead of a massive snowstorm headed to the East Coast, airlines canceled more than 3,000 flights scheduled for Monday and Tuesday. It's making a mess of travel plans before the snow even begins falling. In a few major Northeast hubs, several airlines intend to shut down operations Tuesday. United Airlines and U.S. Airways have already announced their plans to do so at certain airports. The backlog is expected to make traveling a nightmare through the end of the week.